The present invention relates to a storage unit of variable capacity for commodities.
The invention disclosed relates to a storage unit of variable capacity designed for installation in-line between an upstream machine and a downstream machine, such as will accumulate and/or release a variable number of commodities, and in particular packets of cigarettes, to which explicit reference is made throughout the following specification albeit with no limitation in scope implied.
It is standard practice in the tobacco industry for an upstream machine, typically a packer, to be linked to a downstream machine consisting generally in a cellophaner, by way of a variable capacity storage unit able to function as a reservoir for packets passing from the one machine to the other. Such a reservoir is in fact able to compensate both for an interruption or reduction in the supply of packets to the cellophaner, occasioned for example by a stoppage or a momentary drop in tempo of the packer, and for an insufficient uptake of packets turned out by the packer as a result of a stoppage or drop in tempo of the cellophaner.
With a reservoir of variable capacity between the packer and the cellophaner, accordingly, it becomes possible to ensure that a stoppage or drop in tempo of either machine will not adversely affect the operation of the system of which the two machines form a part, at least for a time dependent on the capacity of the storage unit employed.
Finding application to advantage among variable capacity storage units embraced by the prior art is the type identified as first-in-first-out, or FIFO, in which the packets first to be taken up are also the packets first to be released. In familiar FIFO units, the packets advance in an ordered succession along a path extending between a loading station and an unloading station. The number of packets in the storage unit at any given moment, and therefore the capacity of the reservoir, will vary with the variation in ratio between the number of packets fed in and the number of packets released, per unit of time.
One such conventional variable capacity storage unit appears substantially as a single continuous conveyor of helical geometry consisting for example in a flexible power driven belt coinciding with the aforementioned path and capable of advancing the packets from the loading station to the unloading station.
To ensure a continuous supply of packets to the cellophaner when using a storage unit of this type, the appropriate distribution internally of the unit is maintained in such a manner that the packets are ordered in a continuous column; consequently, the capacity of the reservoir is dictated by the length of the path, which can be varied only through the agency of external means such as will allow the positions of the loading station and the unloading station to be moved in relation to the path.
Accordingly, and significantly, in the event that the rate at which the packets are taken up by the cellophaner is slower than the rate at which the packets are turned out by the packer, there will be a call for the reservoir to increase its capacity, with the result that the column of packets forming gradually at the infeed station of the cellophaner, and in the storage unit itself, becomes longer and longer.
The stresses to which the packets making up the column are subjected will increase as the length of the column gradually increases, especially at the end nearest the infeed of the cellophaner; indeed beyond certain limits the consecutive packets will strike one another and the stresses attributable to sliding contact are of an order such as to cause damage to the contents.
It will be clear that first-in first-out storage units of this type betray serious limitations as regards both their capacity and the variation of their capacity, and are able thus to compensate for imbalances in throughput between the machines of a system for short periods only.
The object of the present invention is to provide a storage unit of variable capacity for commodities that will be free of the drawbacks mentioned above, yet simple from the constructional standpoint, in which packets can be transferred from the loading station to the unloading station without suffering damage.
The stated object is realized in a storage unit of variable capacity for commodities, establishing a path along which the commodities are caused to advance between a loading station and an unloading station, characterized in that it comprises at least two conveying members associated each with drive means serving to set the selfsame conveying members in motion, and means by which to link the conveying members in series.